This invention relates in general to the field of electro-optical systems and more particularly to an improved optical switch element and methods of forming and using the element.
The ability to transmit information in the optical domain has greatly enhanced the speed and bandwidth of data communications. In comparison, the inability to selectively route logical signals that are transmitted in the optical domain has restricted the ability of network designers to accomplish data communications solely in the optical domain. Accordingly, before a signal can be routed or switched it must first be converted into electrical signals which can be logically processed using conventional electrical digital computing systems.
There have been a number of attempts to create a workable optical switch architecture which allows for the selective routing of light beams carrying data communications. Some of these solutions have involved the formation of micromechanical structures using semiconductor processing techniques. These micromechanical structures typically do not provide suitable speed or reliability for cost-effective commercial applications. For example, many micromechanical structures suffer from air damping effects, which increase the required drive voltage and slow the operation of the device. In addition, these devices have not been tunable to optimize switching speeds according to common packet sizes encountered by the switch.
Accordingly, a need has arisen for an improved optical switching element and optical switching system that comprises a structure that can be reliably fabricated and that will operate at switching speeds associated with optical data communications.
According to the teachings of the present invention, a micromechanical optical switch element is provided that substantially eliminates or reduces problems associated with prior systems.
In accordance with one embodiment of the present invention an optical switch element comprises a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In one embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.
In accordance with another embodiment of the present invention, an optical switch element comprises a fixed mirror layer disposed outwardly from a substrate, and a movable mirror assembly comprising an inner mirror strip and an outer mirror strip disposed approximately adjacent to and outwardly from the inner mirror strip. In a particular embodiment, the fixed mirror layer and the movable mirror assembly define a Fabry-Perot interference cavity, wherein the movable mirror assembly is operable to move with respect to the fixed mirror layer to change the reflective or transmissive qualities of the switch element.
In accordance with another embodiment of the present invention, an optical switch element comprises a fixed layer disposed outwardly from a substrate, and a unitary movable mirror assembly disposed outwardly from the fixed layer and forming with the fixed layer an optical cavity. The moveable mirror assembly is operable to move relative to the fixed layer in response to a voltage applied to the moveable mirror assembly to affect a change in the transmissive characteristics of the optical cavity. The optical switch element is operable to switch between a substantially transmissive state and a less than substantially transmissive state at a rate optimized for a specified packet size.
According to yet another aspect of the invention, a method of forming an optical switch comprises forming a fixed layer outwardly from a substrate and forming a movable mirror assembly outwardly from the fixed layer. In a particular embodiment, the movable mirror assembly comprises an inner strip disposed outwardly from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.
According to still another aspect of the invention, a method of communicating optical signals comprises receiving an optical signal at an optical switch element having a fixed layer and a moveable mirror assembly disposed outwardly from the fixed layer. In one embodiment, the moveable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The method further comprises applying a voltage to the moveable mirror assembly to change its position relative to the fixed layer and cause a change in the optical transmission of the optical switch element.
In accordance with another embodiment of the present invention, an optical switch includes a Mach-Zender interferometer comprising an optical switch element having a fixed layer disposed outwardly from a substrate, and a movable mirror assembly disposed outwardly from the fixed layer and operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly comprises an inner strip spaced apart from the fixed layer by a first distance; and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.
In accordance with yet another embodiment of the invention, an optical switch comprises a pair of collimating lens each having a central axis and each coupled to a fiber so that the axis of each collimating lens is at least partially offset from the axis of the fiber. The switch further comprises an optical switch clement disposed between the collimating lenses along the central axis of the fiber and spaced from each of the lenses by approximately a focal length of the respective lens, wherein the optical switch element is operable to receive optical signals from one collimating lens and to either transmits those signals to the other collimating lens or to reflect those signals depending on the position of a moveable mirror assembly relative to a fixed layer within the switch element.
In still another embodiment of the present invention, an optical switch, comprises a first optical switch element operable to receive an optical signal and a second optical switch element operable to receive an optical signal, the second optical switch element coupled to the first optical switch element over a first mode. The first and second optical switch elements coupled to a single mode fiber wherein the first mode at least partially overlaps the mode of the single mode fiber so that optical signals from the first and second switch element couple to the fiber only when the first and second switch elements are substantially in phase with one another.
According to another aspect of the invention, an electro-optic router operable to receive and switch a plurality of optical signals, the router comprises a fiber optic tap operable to receive an optical signal and to separate the optical signal into a first signal portion and a second signal portion. The router further comprises a delay line operable to receive the first signal portion and to delay transmission of the first signal portion until the second signal portion has been processed, and an electronic processor operable to receive the second signal portion, and to perform electronic processing on the second signal portion. The router still further comprises an array of optical switch elements operable to receive the first and second signal portions and to perform an optical switching operation on the first and second signal portions.
In another aspect of the invention, an electro-optic router is operable to receive a plurality of optical signals and to switch the optical signals using an array of optical switch elements. At least one of the optical switch elements comprises a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer and operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly comprises an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance, wherein the optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.
In still another aspect of the invention, a fault tolerant network comprises an ingress access node operable to receive an optical signal from a network element external to the fault tolerant network. The fault tolerant network further comprises a fault tolerant node operable to receive the optical signal from the ingress access node and to perform a switching operation on the optical signal depending on a voltage applied to an optical switch element within the fault tolerant node, wherein the fault tolerant node allows transmission of the optical signal when no voltage is applied to the switching element.